This disclosure relates to a semiconductor device and is applicable to, for example, a semiconductor device operating according to a predetermined operation clock.
A microcomputer as an example of a semiconductor device is widely used for the purpose of equipment control. Low power consumption in a semiconductor device is an important challenge to extend a continuous usable time (battery lifetime) and save energy in a portable device. Especially, in a small-sized portable device, it is difficult to set a power device for supplying a sufficient current, by the reason that there are demands for downsizing and price-reduction of a system other than the demand for continuous operation; therefore, a strict limitation is often imposed on the maximum possibly consumable current of a semiconductor device. Further, according to downsizing of equipment, from the viewpoint of a thermal design, it is necessary to minutely control the power consumption.
Briefly speaking, power consumption of a semiconductor device is in proportion to an operating clock frequency. There has been used widely a method of reducing the power consumption by dividing a clock by 1/N (N is a natural number).
As the prior art document related to this disclosure, for example, there is Japanese Unexamined Patent Application Publication No. 2011-114630 or U.S. Pat. No. 8,645,742 corresponding to this.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2011-114630
[Patent Document 2] U.S. Pat. No. 8,645,742